Lead base coating alloy



Patented Oct. 6, 1942 2,298,237 LEAD BASE COATING ALLOY.

Albert A. Smith, Jr., N. J., assignors to and Paul A. Beck, Metuchen,American Smelting and Refining Company, New York, N. Y., a corporationof New Jersey No Drawing. Application March 7, 1941,

Serial No. 382,166

4 Claims.

This invention relates to lead alloys suitable for coating sheet metalor other articles of a different metal base.

The principle of protecting ferrous metal bases from corrosion by theapplication of another metal or alloy thereto is well recognized andunderlies the usual galvanizing and terning practises. However, the lifeof galvanized sheeting is materially shortened by sulphur compounds andthe like commonly occurring in industrial atmospheres and of tin(commonly to in the usual terne-plate constitutes a serious economicthreat to its extended use.

Various proposals have been made to employ lead alloys of much lower tincontent than those ordinarily found in terne-plate but so far as isknown none has proved entirely satisfactory. Thus, a lead-base alloy,containing only a few the relatively high percentage.

per cent of tin with an approximately equal no amount of copper andlesser amounts of antimony and zinc, has been suggested. While suchalloy is considerably cheaper than the high tin alloy, it isdisadvantageous from the standpoints of composition stability, fluiditytemperature, etc.

The present invention provides an alloy composition admirably suited forapplication to ferrous-base sheets or other articles as acorrosionresistant coating; the resulting products being fullycomparable to terne-plate for use in deep stamping operations, roofing,etc., but considerably cheaper than terne-plate from the standpoint ofmanufacturing cost.

Briefly, the invention contemplates the production of a lead-base alloycontaining from l10% tin, 0.2-5% zinc and 0.2-3% antimony, the tin andzinc totalling not less than 3%, and the application of such compositionto a ferrous base such as, e. g., sheet steel. Smooth, continuouscoatings are readily applied using a typical composition of 5% tin, 2%zinc, 1% antimony,

balance lead and coating compositions containing only 2% tin have beensuccessfully used. In general the tin content of the particularcomposition used should be about twice the zinc content to insure ahomogeneous liquid just above the melting point (approximately 700 F.)of the alloy but the tinzzinc ratio can be much lower if a higheroperating temperature (say 800 F.) is employed.

The following table ofiers a comparison, respecting hardness, betweencertain compositions falling within the limits hereinbefore specified,

on the one hand, and commercial lead and a 15% Sn alloy of lead on theother:

' Various procedures may, of course, be employed in applying the alloycoating to the sheets or other articles. Thus, the base may be immersedinto a bath of the desired coating composition through a suitable fluxand then withdrawn by suitable rolls, the thickness and character of thecoating being controlled by the bath temperature, rate of travel of thebase being coated, the position of the driving rolls with respect to thesurface of the bath, and various other operating conditions and factorsknown to those skilled in the art.

Further, the application of the alloy may be varied to produce a varietyof coatings. For example, bright, spangled coatings similar to those ofzinc on steel have been produced by rapidly cooling steel sheets with anair stream just as they emerge from a typical bath containing one percent zinc. For extremely smooth coatings, it has been found beneficialto employ alloys whose zinc content is in the upper part of the range.Obviously, various other modifications and changes in operation may beindulged in by those skilled in the art without departing from the'scopeof the invention.

What is claimed is: V

1. An alloy consisting of 0.2-3% antimony, 0.2-5% zinc, 2-7% tin, andbalance lead.

2. An alloy for coating a ferrous metal base consisting of the followingapproximate composition: tin 5%, zinc 2%, antiniony 1%, balance lead.

3. 'An article of manufacture comprising a ferrous base and a coatingbonded thereto, said coating consisting of 0.2-3% antimony, 0.2-5% zinc,tin,- and balancelead, the zinc and tin totalling not less than 3%.

4. An article of manufacture comprising a ferrous base of sheet metaland a coating bonded thereto, said coating consisting of 24% tin,

0.2-5% zinc. 0.24% antimony. and balance lead.

ALBERT A. SMITH; .m, PAUL A. arzcx.

